Multi-photon induced photo-polymerization provides a means to fabricate three-dimensional devices with exquisite sub-micron resolution in a single processing step. Multi-photon processes involve the simultaneous absorption of two or more photons by an absorbing chromophore. The total energy of the absorbed photons equals the energy of a multi-photon absorption peak, even though each photon individually has insufficient energy to excite the chromophore. Whereas single-photon absorption scales linearly with the intensity of the incident radiation, two-photon absorption scales quadratically. Higher-order absorptions scale with a related higher power of incident intensity. As a result, it is possible to perform multi-photon curing processes with three-dimensional spatial resolution. Furthermore, the excitation radiation is not attenuated by single-photon absorption within a reactive matrix or material, so it is possible to selectively excite molecules at a greater depth within a material than would be possible via single-photon excitation.
Multi-photon fabrication can be used to manufacture mechanical and optical devices, such as cantilevers, gears, shafts, and microlenses. Thus far, however, the technique has been limited to organic polymers. There are many applications where the mechanical, electrical, thermal, and/or optical properties of conventional polymer systems can be inappropriate for the end device use. In other cases, suitable polymer systems can be available, but not easily amenable to photoimaging. In certain applications, there is a need to enhance the physical properties of the completed structures without significantly changing the imaging mechanism.